This is the question i need help with so please help me

What is the value of  y  in the solution to the system of equations? x  +  y  =  12x  –  3y  =  –30a. –8b. –3c. 3d. 8

What is the smallest integer n such that n\sqrt{2} is greater than 20

Ling listed all of the factors of a mystery number: 1,2,4,8,16,32 what is the mystery number?